The present invention relates to an improved method for controlling/asbestos fibers in existing building structures and more particularly to a method for encapsulating and containing the asbestos fibers in existing building structures.
Asbestos present in the walls and ceilings and other existing building structures, such as pipes, ducts, boilers, etc., and insulation surrounding same, constitutes a serious threat to the health of the users of such buildings, which include hospitals, schools, and other public and private accommodations. Airborne asbestos fibers can enter the body and cause asbestois, lung cancer, mesothelioma, and other cancers. Asbestos in buildings can be found on ceilings, walls, and in insulation surrounding hot or cold pipes, ducts, boilers, tanks, and in other asbestos containing materials (ACM). The asbestos can be sprayed onto a surface, troweled onto a surface, or constitute an integral part of the material which is formed into the structure such as ceiling tiles, floor tiles, wall boards, etc. Asbestos that can be crumbled or pulverized with simple hand pressure is considered to be friable and has the greatest potential of becoming airborne asbestos, to which is attributed the health dangers such as mentioned above.
Treatments such as those found in U.S. Pat. No. 4,328,197 to Flowers are applied to the asbestos fibers prior to their incorporation into the types of asbestos products or applications mentioned above. U.S. Pat. No. 4,309,477 to Pezzoli employs a technique that includes spraying an ionizable salt solution onto the asbestos and preferably contacting the asbestos with the ionizable salt solution by slurrying the asbestos in same for a sufficient time to allow the surface of the asbestos to be contacted and wetted by the solution. Thus, Flowers and Pezzoli do not address the problem of dealing with asbestos already contained in existing building structures. Moreover, treatments like these are designed to reduce the level of irritation that the treated asbestos fibers pose to living cells relative to that posed by the untreated asbestos fibers. Such treatments do not necessarily prevent the formation of airborne asbestos fibers.
Actions aimed at correcting or abating the problem of airborne asbestos fibers include removal of the structures containing the asbestos, encapsulation of such structures, or containment of such structures by barrier means.
Removing the asbestos structures is always expensive, involves more exposure to the workers doing the removal, and is not a practical method of abatement for many buildings in which the asbestos forms an integral part of load bearing structures for example. Moreover, the Environmental Protection Agency closely regulates the activities of contractors who perform the removal. The EPA levies fines in excess of $250,000 for violations of federal rules aimed at preventing cancercausing asbestos fibers from being released into the air.
The encapsulation method involves spraying the asbestos material with a sealant to bond the fibers together so as to prevent them from delaminating from the structure and becoming airborne. However, encapsulation typically gives little or limited protection at best from impact with the asbestos structure. Encapsulation is not always effective to prevent the asbestos fibers from delaminating from the substrate and becoming airborne. U.S. Pat. No. 1,850,787 to Brisinqer involves covering wall boards formed of a fibrous composition. The wall boards are completely covered with sheets of fabric, and a thin coat of plastic material is applied to the fabric to provide a finishing surface. The finishing coat is made of an elastic and tough but not brittle material, and a bond is actually formed between the finishing coat and the fabric so that cracks are eliminated regardless of the ordinary distortion of the walls caused by settling of the building, vibration, or other causes. These sheets are adhesively secured to the asbestos wall boards and are firmly secured thereto by a suitable adhesive in the manner substantially the same as wall paper is applied to a wall. The edges of the fabric are preferably laid in abutting relation. The sheets of fabric are preferably a tough cloth fabric such as tough muslin. An example of a suitable plastic material includes a mixture of flat paint with substantially equal parts of plaster of paris and whiting.
Enclosure or barrier containment of the asbestos structures involves building additional containing structures in front of or around the asbestos containing structures. For example, the asbestos is contained by erecting walls that are intended to be air tight so as to contain the asbestos that delaminates or is otherwise freed from the underlying structures. The containment walls are expensive to build and result in a loss of room space. The containment option also can require repositioning various fixtures, such as ceiling lights for example.
U.S. Pat. No. 3,185,297 to Rutledqe, a coinventor of the present invention, discloses a fabric impregnated with uncrystallized gypsum that is formulated so that when it is applied to a substrate with an adhesive, the adhesive causes the gypsum to crystallize and form a secure bond to the substrate. This patent is hereby incorporated herein by reference. U.S. Pat. Nos. 3,887,748 and 3,941,632 to Swedenbero et al, also including one of the coinventors of the present invention, are hereby incorporated herein by reference. The Swedenberq et al patents disclose a wall covering that includes a flexible lath of mesh material bonded to a substantially dry semi-hydrated flexible gypsum layer on one side thereof that is applied to a wall in the manner of wall paper. The walls to which the covering typically is applied include concrete block, concrete walls, cinder block walls, etc. The covering is applied by covering the rear surface of the lath with an aqueous latex adhesive in an amount which will transfer sufficient water from the adhesive to the gypsum to hydrate and set the gypsum and, at the same time, remove sufficient water from the adhesive to invert the latex and convert it to a viscous, tacky state, ideally suited to adhere the wall covering firmly to the substrate. An example of a suitable adhesive is a polyvinyl acetate water emulsion that typically consists of from 45 to 60% solids, the balance being water. The adhesive is applied to an exposed side of the gypsum layer.
In a 1987 technical bulletin published by Wall & Floor Treatments, Inc. of Liberty, S.C., the assignee of the present invention, instructions are provided for applying the Swedenberq et al product such that it should always be brought around outside corners. If inside corners are straight and true, it may also be brought around the corner being sure to force it into the corner to prevent spanning. A clear protective coating comprising polyvinyl butyral is applied by the factory to the surface of the product that will be exposed after attachment to the wall. A clear coating of protective acrylic sealant may be applied after the product has been put on the wall so as to produce a tough, clear low gloss finish that is highly resistant to most common stains, including graffiti.